Blast furnace gas is a gas generated when iron ore is molten to produce pig iron and is used as a fuel gas in blast furnace gas burning gas turbine power generation plants because it contains flammable components. However, because blast furnace gas is typically a low-calorific gas, the gas is often used not alone but as a mixture with, for example, coke oven gas (COG) so that its calorific value can be increased to the level required for burning in gas turbines. Because this calorie-increasing gas has low pressure, a fuel gas compressor is provided in a fuel-gas supply channel leading to a gas turbine combustor so that the gas can be supplied to the gas turbine combustor while being compressed to a high pressure.
On the other hand, because blast furnace gas contains dust, such as iron oxide, and corrosive gas components, the dust is removed by providing a dust collector, such as an electrostatic dust collector, upstream of the fuel gas compressor in the fuel-gas supply channel for supplying blast furnace gas from a blast furnace to a gas turbine facility. Because blast furnace gas contains a large amount of dust, the dust collector used is a wet type dust collector capable of washing away the corrosive gas components together with the collected dust by spraying water.
Patent Document 1 discloses an example of such a blast furnace gas burning gas turbine facility that burns blast furnace gas discharged from a blast furnace by supplying the gas to a combustor after removing a large amount of dust contained in the gas with a wet type dust collector and compressing the gas with a fuel gas compressor. In the facility disclosed in Patent Document 1, excess fuel gas discharged from the fuel gas compressor during low-load operation is returned to the inlet side of the dust collector via a flow control valve and a fuel gas cooler.
Patent Document 1:    Japanese Unexamined Patent Application, Publication No. HEI-9-79046